Sealed beam lamp



April 29, 1952 R N, FALGE 2,594,753

SEALED BEAM LAMP Filed 0G13. 6, 1949 uventor (ttornegs Patented pr. 29,1952 SEALEDi BEAM LAMP I-tobert N, Falgc, Andersomlnd., assignor toGeneral Motors Corporation, Detroit, Mich., a corporation of DelawareApplication october s, 1949, serial No. 119,925

The present invention relates to vehicle lamps and particularly to lampsof the type comprising a metal reector, a lamp bulb and a lens sealed asa unit,` such lamps being commonly known assealed beam lamps. Y.

Heretofore Athe sealing of suchlampunits has been accomplished byclamping the lens and reflector flanges on 'an interposed .rubber gasketcured to provide optimum elasticity and toughness. Such rubber gasketswould deform `to receive projecting flanges in the lens and-reiiectorbut would not grip or adhere to the lens and metal reflector andconsequently with aging or misalignment of lensand reector they.permitted the passage of air and containedmoisture causing condensationon the inner lens .surface and a reduction of reflection efciency of thereflector surface.V

Accordingly it is an object of the present invention to provide animproved lamp unit vconstruction of the sealed beam typewhich has a highdegree of resistance to leakage over indenite periods of time.y

This and other` objects are attained in accordance with the presentinvention by providing a lamp unit construction having a sealing gasketof natural rubber characterized by a core of tough elastic cured rubberand a surface coating of a tacky or adhesive rubber constituent formedby a curing process known as reversion. Reversion as it is commonlyknown involves the heating of masticated rubber which has been mixedwith sulphur. There is an improvement in mechanical properties asheating is continued until an optimum is reached. Thereafter withcontinued heating the physical properties decline, strength decreasesand the rubber becomes shorter and shorter. If the heating is carriedfurther the rubber becomes tacky and plastic. Advantage of thischaracteristic is taken in the present invention to provide a lamp unitconstruction in Which'van overcured rubber gasket provides means for avsubstantially air-tight seal over indefinite periods of time.

For a better understanding of the invention reference may be had to theaccompanying drawing in which Figure l isa side elevation view of a lampunit embodying the present invention, and Figure 2 is an enlargedcross-sectional view in perspective of a fragment of thev 12 oiai'ms.(o1. 31a- 113) the lens to the reiiector with a rubber gasket 8interposed therebetween. The reector flange is formed with a radiallyextending portion I!! and an axially extending portion I2 of sufficientlength to be turned inwardly on ythe annular ange i4 of the lens. Thelens flange i4 is provided witli axially extending annular projectionslwhich cooperate with the gasket 8 and a similar axially extendingannular ridge i8 on the reflector flange to form the seal for the lensand reflector.v

The gasket 8 is a natural rubber material which as has been hereinbeforeindicated may be heat-treated to provide a tacky or adhesive surfacewhich not only conforms to the contours ofnthe surfaces of'fianges IQand i4 but adheres to the vsurfaces of the anges.

,Tobprovide the tacky,l or adhesive surface the assembled reflector 2and bulb i is placed on a traveling belt with the reflecting faceupwardly. The gasket 8 of natural rubber which is substantially free ofvolatile material is placed in positionon the flange I!! and passes withthe reector assembly into a furnace which is heated tov a temperature of360 to 380 F. The furnace and belt speed are arranged so that after atime interval of `seven minutes the gasket and reiiector assembly vpassa station where the lens is placed in position on the gasket andthereafter the reflector assembly, gasket and lens continue in thefurnace for an additional three minutes. Thereafter the axiallyextending portion l2 of the reflector flange is bent inwardly on thelens flange I4 sealing the lamp assembly as a unit.

With the heat-treatment above described the gasket material reverts to atacky or adhesive vstate on the surfaces thereof and to a suicientdepth. to permit the plastic surface constituent to conform to theprojections I6 and ridge I3 adhering with considerable tenacity to allflange surfaces in contact with the gasket. The core of the'gasketremains tough and elastic being substantially unaffected by theheat-treatment. With such a heat-treatment the gasket provides optimumsealing characteristics while retaining a high degree of elasticity andstrength at the core i, to `withstand permanent deformation. With such agasket. treated in the manner described, I have found that the lampunits remain impervious to the atmosphere over indefinite periodsoftime.

While I have disclosed a preferred embodimentu'of the present invention,it is to be understood that other forms might be adopted, all comingwithin the scope of the claims which follow:

vWhat I claim as new and desire to secure by LettersPaten-t of theUnited States is:

l 1. In a unitary lamp in combination, a reector, alarnp bulb attachedtosaid reector, a lens clamped to said reflector and a gasket interposedbetween said reflector and said lens, said gasket having a tough elasticcore and an adhesive or tacky surface for adhesively bonding said gasketto said lens and reflector surfaces to seal said lamp against theadmission of atmosphere.

2. In a unitary lamp in combination, a reilector, a lamp bulb attachedto said reflector with its filament substantially coinciding with thefocal axis of said reflector, a lens clamped at its annular edge to saidreflector, a cured rubber gasket interposed between said reflector andsaid lens, said gasket having been heat-treated to provide an adhesiveor tacky reverted rubber surface for adhesively bonding said gasket tothe engaging surfaces of said lens and reflector and seal said lampagainst the admission of atmosphere therein.

3. In a unitary vehicle lamp in combination, a metal reflector having anannular clamping flange thereon, a lamp bulb having its base attached tosaid reflector to provide substantial alignment of its filament and thefocal axis of said reector a substantially air-tight seal between saidbase and said reflector, a lens clamped to said reflector by said flangeand a heat-treated natural rubber gasket interposed between saidrellector and said lens, said gasket having a tough, elastic curedrubber core and a tacky, adhesive, reverted rubber portion surroundingsaid core for adhesively bonding said gasket to the engaging surfaces ofsaid reflector and said lens to provide a substantially air-tight seal.

4. In a vehicle lamp unit in combination, a substantially parabolicmetal reflector having an annular clamping flange with an axiallyextending ridge, a lamp bulb having its base attached to said reflectorto provide a substantially air-tight seal, said bulb having its lilamentin substantial alignment with the focal axis of said reflector, a lenshaving an annular flange with axially extending projections clamped tosaid reflector by said ange, and a heattreated natural rubber gasketinterposed between said reflector and said lens, said gasket having atough, elastic cured rubber core and a reverted rubber portionsurrounding said core to provide a tacky, adhesive surface for receivingsaid ridge and said projections and adhesively bond said gasket to theengaging surfaces of said reflector and lens to provide a substantiallyair-tight seal.

5. The process of sealing a unitary lamp assembly comprising a metalreflector, a lamp bulb and a lens which includes interposing a naturalrubber gasket between said reflector and lens, heating said gasket toform a tough elastic cured rubber core surrounded by a tacky adhesivesurface layer of reverted rubber and clamping said gasket between saidreflector and lens to cause said surface layer to adhesively bond saidgasket to the engaging surfaces of said reflector and said lens.

6. The process of sealing a unitary lamp assembly comprising a metalreflector with an annular flange, a lamp bulb attached to said reflectorand a lens which consists of placing a natural rubber gasket on theannular flange of said deflector, subjecting said reflector and gasketto a temperature of about 360 to 380 -F. for about seven minutes tocause a revision of the rubber at the surface of said gasket, placingsaid lens with its annular edge in engagement with said gasket, furtherheating said lens, reflector and gasket at about 360 to 380 F. for aboutthree minutes to cause further reversion of the rubber adjacent thesurface of said gasket and thereafter clamping said lens and reflectortogether on the adhesive or tacky reverted rubber surfaces formed onsaid gasket.

7. A gasket for positioning between the lens and reflector of a unitarylamp assembly including a reflector, lens and light source, said gasketcomprising a tough, elastic core surrounded by adhesive or tacky surfaceportions for adhesively bonding said gasket to said lens and reflectorsurfaces to seal said lamp against the admission of the atmosphere.

8. A rubber gasket for positioning between the lens and reflector of aunitary lamp assembly including a lens, reflector and light source toseal said assembly against the admission of the atmosphere, said gasketcomprising a tough elastic cured rubber core surrounded by revertedrubber portions providing tacky surfaces for adhesively bonding saidreflector and lens.

9. An annular rubber gasket for positioning between the lens andreflector of a unitary lamp assembly including a lens, reflector andlight source to seal said assembly against the admission of theatmosphere, said gasket comprising a tough elastic core of cured naturalrubber surrounded by a layer of reverted natural rubber providing tackygasket surfaces for adhesively bonding said gasket to the engagingsurfaces of said reilector and lens.

10. An annular rubber gasket adapted to be interposed between the lensand reflector of a unitary lamp assembly commonly known as a sealed beamlamp, said gasket comprising a tough elastic core of cured naturalrubber surrounded by a layer of permanently reverted natural rubberproviding tacky gasket surfaces for adhesively bonding said gasket tothe engaging surfaces of said reflector and lens.

1l. In a unitary lamp assembly having a lens, reflector and lightsource, a gasket for positioning between said lens and reflector, saidgasket comprising a tough, elastic core of cured rubber surrounded by alayer of permanently reverted rubber providing tacky gasket surfaces foradhesively bonding said gasket to said lens and reflector to seal saidassembly against the admission of the atmosphere.

12. The process of sealing a unitary lamp assembly comprising a metalreflector with an annular flange, a lamp bulb attached to said reflectorand a lens, said process comprising the steps of placing a naturalrubber annular gasket on said flange, positioning said lens on saidgasket, heating the assembly to a temperature and for a period of timeto provide said gasket with a tough elastic core of cured rubber and asurrounding layer of tacky reverted rubber and thereafter clamping saidlens, gasket and reflector together to adhesively bond said gasket tothe engaging surfaces of said lens and reflector to seal said assemblyagainst the admission of the atmosphere.

' ROBERT N. FALGE'.

REFERENCES CITED The following references are of record in the file ofthis patent:

Dana Apr. 20, 1943

